3 Humidity

The water vapor in the air will be adsorbed on the surface of the paper and the ink layer to prevent the contact of oxygen and ink, so that the oxidative polymerization of the ink is blocked, resulting in slow drying. When the relative humidity is 85% and 65%, the drying speed of the printing ink layer will be doubled. When the humidity is more than 95%, the difference will be 2 to 5 times.

4 temperature

Heat is one of the conditions that initiate and promote the oxidative polymerization. The oxidative polymerization of dry oil is itself an exothermic reaction. Therefore, the temperature has a great influence on the ink drying. For example, when the temperature is 25°C, it is dry compared to 15°C. Speed ​​can be doubled as fast.

5 humidity

The moisture can delay the drying of the ink, and the acidic substances in the wetting liquid can work with the metal salts in the desiccant to reduce the lyophilization. Therefore, the pH of the wetting liquid has an effect of not more than 5.5, which is not significant. To 4.5 or less will make the drying time double, when the PH value of 3.5 or less, plus a large amount of water, ink emulsification is serious, it will cause the ink does not dry for a long time.

6 Drying and paper pH

One is that the surface structure of the paper is related to the fixation of the ink. Drying of the conjunctiva and paper with too high water absorption will draw a large amount of dry oil and synthetic resin into the ink, so that the surface of the ink is not dry and the resin cannot be formed. The firm film layer, so that heavier touch or friction will be wiped off, printing called powdering. Second, due to different manufacturing processes, the paper also has different pH values. Alkalinity is beneficial to ink drying, and acidity is not conducive to ink drying. In addition, in the practice of offset printing production in China for less than 20 years, it is often preceded by a printed spot color in order to contrast the theme picture. In order to achieve the purpose of bright and bright background, the ink layer is usually printed thick or printed twice. Dry oil also added more. Because the ink layer completely covers the paper, and the drying is too fast, the surface of the ink layer often becomes a very smooth film layer, like the glass, resulting in the second color printing is not on, even if the printing is not attached to the phenomenon is called the ink film Crystallized or called vitrification. The ink film is already crystallized. To print the second color, there are two methods in principle: one is to enhance the adhesion of the second color ink; the second is to destroy the crystallized ink film, alkyd, epoxy, Polyamide resin is a material with a large adhesion, or the addition of a tackifier resin to the ink, can increase its adhesion, but these resins are not miscible with the ink. So can not be added, adding more to dilute the color hue of the ink. The third is to add an organic strong solvent to the ink to dissolve the vitrified ink film. This is a method used by printing operators for many years. However, the smooth film layer that has become a three-dimensional mesh structure due to the crystallized ink layer is not easily dissolved, so the effect is also Not so good, some add alkali in the ink, soap to enhance its polarity, so that it is easier to print, but at that time it has been printed, after drying it is not firmly attached, easy to wipe off. In recent years, coupling agents and tackifying resins have mostly been used together to solve problems, and the effect is very good. There is also a large area of ​​all overprinting of a transparent ink or zero varnish or resin polish oil, which does not wait for it to dry to print the second color ink, the effect is more likely. However, this method is labor-intensive, time-consuming, wasteful, and costly.

11. High-speed drying

First, the use of high-efficiency dispersants in the ink to make the printing ink film layer dense and thin ink layer, both conducive to fixing and drying, but also to improve the stain on the back of the print, etc.; The second is to add kerosene and alcohol in the ink The method (about 75:25) and the method of mixing starch and talcum powder are all effective ways to increase the drying speed of offset ink. Another example is the use of dimethylester (DBE) in the past one year to increase the molecular weight of the ink, which in turn improves the gloss of the kerosene, resulting in poor gloss and penetration of the backside.

Note: In order to achieve instantaneous drying, conditions can be used UV printers to print aluminum foil and gold and silver substrates (using UV light solid ink).